In spite of rapid advances in the fields of cardiology and cardiac surgery and in the use of cardiac assist devices, the mortality rate from cardiogenic shock associated with myocardial infarction remains objectionably high. Additionally, there is the rate occurrence of inadequate cardiac function at the termination of cardiopulmonary bypass. In response to these needs for improved cardiac assist devices, Donald and McGoon in 1971 described a simple device that could provide an exogenous energy source to supplement deficient myocardial performance, could be autoregulatory and would not itself interfere with cardiac recovery. They further proposed that this device, the intraventricular balloon, might be particularly useful in profound cardiogenic shock when the intra-aortic balloon is ineffective. Studies in our laboratory have indicated that in the presence of profound shock, use of the intraventricular balloon improves cardiac output, increases systematic arterial pressure and decreases left atrial pressure. Studies in normal calves indicate that short term (3-4 hours) intraventricular balloon pumping has no detrimental effects on hemodynamics and results in no significant pathological sequelae. Based on these data, we propose to continue studies with the intraventricular balloon (IVB) to: (1) determine the hemodynamic and pathologic effects of prolonged (5 days) IVB pumping in calves, (2) determine the distribution of cardiac output during IVB pumping and compare these data to those obtained during intra-aortic balloon pumping, (3) initiate studies of the effectiveness of the intraventricular balloon in patients who have inadequate cardiac function to support life at the termination of cardiopulmonary bypass and in patients in cardiogenic shock following myocardial infarction in whom intra-aortic balloon pumping is ineffective. Data obtained from these studies will indicate the effectiveness of intraventricular balloon pumping in improving effective cardiac output, maintaining systemic pressure and reducing left atrial pressure. Proof of the effectiveness of this device in man would permit widespread use of a cardiac assist device more effective than those currently available.